Sulphuric acid mist

Photometric determination. The sulphuric acid aerosol captured on a paper or membrane filter and dissolved in water releases from insoluble barium chloranilate an equivalent amount of red-violet chloranilate ions, which are suitable for a spectrophotometric determination [18]. 

Nephelometric and turbidimetric determination. The sample is collected in a bubbler containing water and isopropanol, and the sulphate content is determined turbidimetrically or nephelometrically after addition of BaClj [13]. 

A further possibility for determining sulphuric acid is based on the classical method involving titration with sodium hydroxide. 

Spectrophotometric determination. Hydrogen sulphide is captured in a zinc acetate solution with an admixture of N, JV-dimethyl-p-phenylenediamine and an iron(III) salt, forming Methylene Blue. This compound is determined by spectrophotometry at 670 nm [20]. 

Carbon disulphide reacts with diethylamine to form diethyldithiocarba-mate, which yields a yellow-brown colour with copper ions, 

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Sulphuric acid mist and SO, from stationary sources 8... 

Griffiths, R. (ed.) (1995) Sulphur Trioxide, Oleum and Sulphuric Acid Mist, Institution of Chemical Engineers, Rugby. Hamngton, J.M. and Gardiner, K. (1995) Occupational Hygiene, 2nd edn, Blackwell Science, Oxford. 

The regulations concerned with exposure limits to various substances vary around the world. However the Occupational Health and Safety Authority (OSHA) and the American Conference of Government Industrial Hygienists (ACGIH) set the most commonly applied regulations and guidelines used. With reference to sulphuric acid mist, the current OSHA/ACGIH requirements are ... 

Table 2.5 Techniques for reduction of sulphur trioxide and sulphuric acid mist ...

During the transfer of the Pyrosuphate salt of Dimethyl Sulphate and Sulphur Trioxide from the pryo reactor to the next stage reactor, a PTFE lined braided stainless steel tranter hose developed a leak. Approximately, 400 Kg (900pounds) of pyrosulphate was released to the plant sump. The material reacts with water and a cloud of Sulphuric acid mist was generated. 

Electrostatic precipitation Very fine droplets can be charged and then attracted to collecting plates Has been used to remove sulphuric acid mist from gaseous effluent. See discussion... 

Figure 1 illustrates the overall block diagram. To raise S03/air with a volumetric content between 4 and 7% SO3, the process air should be dried to prevent the formation of sulphuric acid mist. Filtered ambient air is compressed (about 0.6 bar gauge), chilled (about +5 C) to remove the major part of water by condensation and subsequently dried with a desiccant (silica gel. Alumina) to arrive at a process air dewpoint of about -60 C. 

The failure of a filling or unloading line attached to a road tanker of, say, 18 ton, capacity has been identified as an event which is representative of the foreseeable sizes of release from a typical installation. Severance of the line, e.g. by tanker moving while it is being filled or unloaded, would cause the release of sulphur trioxide. The SO3 released will spread in a pool, reacting violently with any water present, either in or on the ground, until all the water is used up. The result will be the production of a large cloud of dense sulphuric acid mist. Once the readily available water has been used up, the pool of sulphur trioxide will continue to emit sulphuric acid mist fumes from reaction with moisture in the air. This will continue until all the sulphur trioxide is used up or remedial measures have been taken. Trials by ICI with 65% oleum... 

It has been calculated that a spill during tanker filling or unloading operation as outlined above could release approx. 1.0 ton of SO3 as sulphuric acid mist, which would form the initial cloud. As the cloud is blown along by the wind, it will be diluted by entrained air until the concentration is no longer hazardous. The distance to this point will depend on the wind and weather conditions. In stable weather conditions (Pasquill category D and at 5 m/s windspeed) a dispersion model predicts that the clouds could be hazardous up to about 1 kilometre from the point of release ... 

Sulphur trioxide frimes form oleum with atmospheric moisture. The exposure to sulphuric acid mist has been described to some extent in section 3.3.1. Hazards of sulphur trioxide. 

Unconverted SO2, unreacted SO3 (partly as sulphuric acid mist) and entrained organic acid mist droplets are present in the exhaust gas and are the main potential atmospheric pollutants. The sulphur dioxide is due mainly to the incomplete conversion of SO2 to SO3. A small proportion of SO2 may arise from the sulphonation reaction itself but generally the amount of SO2 in the waste gas is a direct function of SO2 converter efficiency. 

The exhaust gas leaving the ESP, virtually free from any organic acid and sulphuric acid mist, enters the SO2 scrubber made of acid-proof construction material. The caustic scrubber equipment consists of ... 

Sulphuric acid mist removal from exhaust gas... 

Sulphuric acid mist levels are directly related to the dew-point of the dried air (see 5.2.2.). Ihe sulphuric acid mist is effectively removed in the ESP and levels smaller than 10 mg/m ar guaranteed by ESP suppliers (see also 5.9.1. and 5.9.3.). Very small amounts of gaseous SO3 will pass the ESP but will be trapped in the caustic soda scrubber. 

The sampling train consists of a plastic filter holder fitted with a 47mm Whatman GF/A glass fibre filter paper to trap sulphuric acid mist and organic acid mist, followed by three bubblers connected in series, each one fitted with a number 2 porosity sintered glass globe on the inlet pipe. 

SO2 stationary conditions SO2 start up conditions Sulphuric acid mist Organic acid mist... 

Assume that sulphuric acid mist and organic mist are completely trapped in ESP. 

The other environmental problem is due to hydrocarbon impurities and is greatest when dark sulphur is used. It is caused by the water vapour from combustion of the hydrocarbons reacting with sulphur trioxide to form a sulphuric acid mist. The amount of mist produced is lowered if bright sulphur is used and is almost eliminated by absorption of sulphur trioxide with 98% sulphuric acid instead of water. 

It is important that aU the gases of SO3 are absorbed in the Sulphuric Acid Sparger and the Sulphuric Acid mist is removed by cyclone separator as well as mist eliminator and traces are trapped in Coke Tower. 

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